The overall objective of this project is to determine how small molecules and their metabolic products affect rhe stability and function of hemoglobin and red blood cells. Goals for the current year were to study the oxidation of derivatives of phenylhydrazine and the reaction of these derivatives with hemoglobin with particular reference to their role in the production of hemolysis. Research goals for the coming year are: (A) To continue the study of the mechanism of reaction of aryldiazenes with the heme iron of ferrihemoglobin; (B) To study the effect of substituents on the phenyl ring on the reactivity of nitrosobenzene with ferrohemoglobin; (C) To complete the oxygen equilibrium apparatus and study the effect of aryldiazenes on oxygen equilibrium of hemoglobin. Hemoglobin S will be reacted with reagents other than cyanate, and effect of such reactions on solubility of this hemoglobin will be examined.